Britney Spears has performed nearly 100 shows at Planet Hollywood Las Vegas since the release of her eighth studio album, 2013's Britney Jean. And though the singer has been back in the studio as far back as September, don't expect a proper follow-up anytime soon. "I'm gonna do [a new album] slowly but surely," Spears tells Billboard for the latest cover story, on stands Friday, March 13. "There's a lot going on with my kids and schools and, you know, adding new sports and stuff like that. I'm